Bug Description

When attempting to initialize pythoscope against a file such as urlparse.py in the standard library, an ASTError("Unknown node type: (") exception is raised. This can easily be reproduced by runing pythoscope -i on the following class:

class Example(namedtuple('a')):
pass

The exception is raised on line 76 of astvisitor.py.

Attached is debug output with a detailed stack trace and the exact node that caused the problem. I've also attached a patch to test/test_static_inspector.py which uncovers this specific error.